1. Field of the Invention
The invention relates to a display device having an optical display field in which a first light source is arranged behind the display field, where the light source is configured so as to generate an elementary color or a secondary color from the elementary colors red, green and blue, and where the first light source is connected to an activation module and the activation module is configured to activate the first light source in accordance with the color to be generated.
2. Description of the Related Art
Display devices are preferably used in automation technology to automate industrial processes. Here, the display devices are preferably configured as control and observation devices or Human Machine Interface (HMI) devices. Furthermore, the display devices can be embodied as key panels or pushbutton panels. The key panels or pushbutton panels generally comprise illuminated push-buttons for machine operation. These display devices and/or panels are preferably designed for direct machine operation. As a result, they are preferably connected to a programmable logic controller by a field bus, such as a Profibus or a Profinet. Display devices of this type are essentially used to relay a machine status in the form of color information and to receive information in the form of pushed or keyed buttons on the display device.
With buttons that are configured as illuminated pushbuttons, the five colors red/green/blue/yellow/white can preferably be represented on account of the RGB LED used. In this way, yellow and white represent secondary colors. Yellow is produced from red and green, white is produced from red and green and blue.
If a fault occurs on one of the LEDs, the color information to be reproduced is distorted. The user or a machine operator may then interpret the machine status incorrectly. Particularly in automation technology, i.e., in safety-oriented automation technology, the color information yellow is interpreted as an abnormal status (also see International Electrotechnical Commission/European (IEC/EN) standard 60204-1.